Low Temperature Lesion Formation Apparatus, Systems And Methods

ABSTRACT

Low temperature lesion formation apparatus, systems and methods. The apparatus includes a base member and an inflatable element carried by the base member.

BACKGROUND OF THE INVENTIONS

1. Field of Inventions

The present inventions relate generally to devices for performingtherapeutic operations on body tissue.

2. Description of the Related Art

There are many instances where therapeutic elements must be positionedadjacent to body tissue. One instance involves the formation oftherapeutic lesions to the treat cardiac conditions such as atrialfibrillation, atrial flutter and arrhythmia. Therapeutic lesions, whichmay also be used to treat conditions in other regions of the body suchas the prostate, liver, brain, gall bladder, uterus, breasts, lungs andother solid organs, are typically formed by ablating tissue.

Cryogenic cooling devices are one example of the devices that have beenused to form lesions in tissue. During the cryo-ablation of soft tissue(i.e. tissue other than blood, bone and connective tissue), ice crystalsdisrupt cell and organelle membranes and it is the disruption that killsthe tissue. A cryogenic element, such as a balloon or hollow metal tip,is carried on the distal end of a catheter or surgical probe (referredto herein collectively as “probes”), placed in contact with tissue andcooled to a temperature that will cause tissue death. The cryogenicelement may be cooled by a variety of techniques. One technique employsthe Joule-Thompson (“JT”) effect. Here, cryogenic cooling occurs as aresult of a rapid decrease of gas pressure that occurs within thetherapeutic element. Pressurized cryogenic fluid, such as liquid nitrousoxide, is directed into the therapeutic element where it undergoes rapidphase change and a rapid expansion of the gas from a high-pressure to alower pressure state. The reaction is endothermic and producestemperatures as low as minus 70° C. at the therapeutic element. In someinstances, the cryogenic fluid is pre-cooled in order to increase thecooling power delivered to the targeted tissue. The cryogenic elementmay also be cooled by directing super-cooled fluid through the catheteror surgical probe to the cryogenic element. Here, the temperature at thetherapeutic element can be as low as minus 100° C. when it enters thepatient.

The present inventors have determined that conventional cryogeniccooling devices are susceptible to improvement. For example, the presentinventors have determined that conventional cryogenic cooling devicescan damage non-target tissue near the tissue in which the therapeuticlesions are being formed. The present inventors have also determinedthat it can be difficult to achieve good tissue contact withconventional cryogenic devices because they are relatively turgid. Someconventional cryogenic cooling devices are susceptible to leaks, whichcan result in the release of toxic chemicals (e.g. perfluorocarbons)into the patient's blood stream during endocardial procedures.Additionally, the inventors herein have determined that the manner inwhich temperature is monitored during cryogenic lesion formationprocedures.

SUMMARY OF THE INVENTIONS

An apparatus in accordance with one invention herein includes a basemember, an inflatable cryogenic element carried by the base member and aconnector, associated with at least one of the base member and theinflatable cryogenic element, adapted to maintain the inflatablecryogenic element in the looped orientation. A system in accordance withone invention herein includes such an apparatus and a source ofcryogenic fluid. A method in accordance with one invention hereinincludes the steps of positioning an apparatus including an inflatablecryogenic element in a looped orientation around a tissue structure,securing at least two portions of the apparatus relative to one anotherto maintain the looped orientation and directing cryogenic fluid throughthe inflatable cryogenic element.

An apparatus in accordance with one invention herein includes aninflatable cryogenic element and a base member that carries theinflatable cryogenic element, is pre-shaped into a loop configuration,and is bendable into a non-loop configuration. A system in accordancewith one invention herein includes such an apparatus and a source ofcryogenic fluid. A method in accordance with one invention hereinincludes the steps of bending an apparatus including an inflatablecryogenic element into a looped orientation around a tissue structurewith a pre-shaped portion of the apparatus, maintaining the apparatus inthe looped orientation and directing cryogenic fluid through theinflatable cryogenic element.

An apparatus in accordance with one invention herein includes aninflatable cryogenic apparatus configured to be removably secured to afirst clamp member and a temperature sensor apparatus configured to beremovably secured to a second clamp member. A clamp in accordance withone invention herein includes first and second clamp members, aninflatable cryogenic apparatus carried by the first clamp member, and atemperature sensor apparatus carried by the second clamp member. Systemsin accordance with inventions herein include a source of cryogenic fluidand the apparatus or the clamp. A method in accordance with oneinvention herein includes the steps supplying cryogenic fluid to acryogenic apparatus on the first opposing surface and measuringtemperature on the second opposing surface.

An apparatus in accordance with one invention herein includes a basemember configured to be removably secured to a clamp member and aninflatable cryogenic element, carried by the base member, defining alongitudinal axis and a non-circular inflated shape in a cross-sectionperpendicular to the longitudinal axis. A clamp in accordance with oneinvention herein includes a cryogenic apparatus including an inflatablecryogenic element defining a longitudinal axis and a non-circularinflated shape in a cross-section perpendicular to the longitudinalaxis.

A method in accordance with one invention herein includes the steps ofpositioning a resilient inflatable cryogenic element adjacent to tissue,inflating the resilient inflatable cryogenic element with cryogenicfluid and maintaining pressure within the resilient inflatable cryogenicelement below about 100 mm Hg. A system in accordance with one inventionherein includes a source of cryogenic fluid and resilient inflatablecryogenic element adapted to be operably connected to the source ofcryogenic fluid. The pressure within the resilient inflatable cryogenicelement is maintained below about 100 mm Hg when the source of cryogenicfluid supplies the cryogenic fluid to the resilient inflatable cryogenicelement.

An apparatus in accordance with one invention herein includes aresilient inflatable cryogenic apparatus configured to be removablysecured to a clamp member and to operate at a maximum internal pressureof about 100 mm Hg. A clamp in accordance with one invention hereinincludes a resilient inflatable cryogenic apparatus configured tooperate at a maximum internal pressure of about 100 mm Hg.

A surgical probe in accordance with one invention herein includes arelatively short shaft, an inflatable cryogenic element defining anexterior surface, and at least one temperature sensor on the exterior ofthe inflatable cryogenic element.

A method in accordance with one invention herein includes the steps ofpositioning an inflatable cryogenic element on the tissue structure witha temperature sensor between a portion of the inflatable cryogenicelement and a portion of the tissue surface, supplying cryogenic fluidto the inflatable cryogenic element, and measuring tissue temperaturewith the temperature sensor.

A surgical probe in accordance with one invention herein includes arelatively short shaft and a resilient inflatable cryogenic element,carried by the relatively short shaft, and configured to operate at amaximum internal pressure of about 100 mm Hg. A system in accordancewith one invention herein includes such a surgical probe. A method inaccordance with one invention herein includes the steps of positioning aresilient inflatable cryogenic element on the tissue structure with asurgical probe, inflating the resilient inflatable cryogenic elementwith cryogenic fluid and maintaining pressure within the resilientinflatable cryogenic element below about 100 mm Hg.

There is a wide variety of advantages associated with the presentinventions. By way of example, but not limitation, and as described indetail below, at least some of the present inventions prevent damage tonon-target tissue near the tissue in which the therapeutic lesions arebeing formed. As described in detail below, at least some of the presentinventions achieve superior tissue contact because they are relativelyresilient. As described in detail below, at least some of the presentinventions are especially useful in applications outside the bloodstream (such as epicardial applications) where leaks are less likely toharm the patient. As described in detail below, because at least some ofthe present inventions are configured to operate at relatively lowpressure, the volume of cryogenic fluid that is lost in the unlikelyevent of a leak will be lower than conventional devices which operate athigh pressure. As described in detail below, at least some of thepresent inventions provide superior temperature monitoring capabilities.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed description of preferred embodiments of the inventions will bemade with reference to the accompanying drawings.

FIG. 1 is a side view of a lesion formation apparatus in accordance witha preferred embodiment of a present invention.

FIG. 2 is a section view taken along line 2-2 in FIG. 1.

FIG. 3 is a section view taken along line 3-3 in FIG. 1.

FIG. 4 is a perspective view showing a surgical system including thelesion formation apparatus illustrated in FIG. 1.

FIG. 4A is perspective view showing a continuous lesion formed aroundthe pulmonary veins.

FIG. 5 is a section view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 6 is a section view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 7 is a section view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 8 is a section view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 8A is a section view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 8B is a partial side view of a lesion formation apparatus inaccordance with a preferred embodiment of a present invention.

FIG. 8C is a partial section view taken along line 8C-8C in FIG. 8B.

FIG. 8D is a side view of the lesion formation apparatus illustrated inFIG. 8B in a loop orientation.

FIG. 9 is a side view of a lesion formation apparatus in accordance witha preferred embodiment of a present invention.

FIG. 10 is a section view taken along line 10-10 in FIG. 9.

FIG. 11 is a section view taken along line 11-11 in FIG. 9.

FIG. 12 is a partial section view taken along line 12-12 in FIG. 11.

FIG. 13 is a side view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 14 is a section view taken along line 14-14 in FIG. 13.

FIG. 15 is a section view taken along line 15-15 in FIG. 13.

FIG. 16 is a partial section view taken along line 16-16 in FIG. 15.

FIG. 17 is a side view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 18 is a section view taken along line 18-18 in FIG. 17.

FIG. 19 is a partial section view taken along line 19-19 in FIG. 17.

FIG. 20 is a section view taken along line 20-20 in FIG. 19.

FIG. 21 is a side view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 22 is a top view of a portion of the lesion formation apparatusillustrated in FIG. 21.

FIG. 23 is a bottom view of a portion of the lesion formation apparatusillustrated in FIG. 21.

FIG. 24 is a side view of the lesion formation apparatus illustrated inFIG. 21 in a looped orientation.

FIG. 25 is a side view of a lesion formation apparatus in accordancewith a preferred embodiment of a present invention.

FIG. 26 is a section view taken along line 26-26 in FIG. 25.

FIG. 27 is a side view of a portion of a lesion formation apparatus inaccordance with a preferred embodiment of a present invention.

FIG. 28 is a side view of a portion of a lesion formation apparatus inaccordance with a preferred embodiment of a present invention.

FIG. 29 is a section view taken along line 29-29 in FIG. 28.

FIG. 29A is a side view of a portion of a lesion formation apparatus inaccordance with a preferred embodiment of a present invention.

FIG. 29B is a section view taken along line 29B-29B in FIG. 29A.

FIG. 30 is a side view of a portion of a lesion formation apparatus inaccordance with a preferred embodiment of a present invention.

FIG. 31 is a side view of a portion of the lesion formation apparatusillustrated in FIG. 30.

FIG. 32 is a side view of a portion of a lesion formation apparatus inaccordance with a preferred embodiment of a present invention.

FIG. 33 is a perspective view of a surgical system in accordance with apreferred embodiment of a present invention.

FIG. 34 is a plan view of a tissue coagulation assembly in accordancewith a preferred embodiment of a present invention.

FIG. 35 is a section view taken along line 35-35 in FIG. 34.

FIG. 36 is a section view taken along line 36-36 in FIG. 34.

FIG. 37 is a section view taken along line 37-37 in FIG. 34.

FIG. 38 is an enlarged view of a portion of the tissue coagulationassembly illustrated in FIG. 34.

FIG. 39 is a section view taken along line 39-39 in FIG. 38.

FIG. 40 is a section view taken along line 40-40 in FIG. 38.

FIG. 40A is a section view taken along line 40A-40A in FIG. 38.

FIG. 41 is a plan view of a clamp in accordance with a preferredembodiment of a present invention.

FIG. 42 is a section view taken along line 42-42 in FIG. 41.

FIG. 43 is a top view of a portion of the clamp illustrated in FIG. 41.

FIG. 44 is a perspective view of a surgical system in accordance with apreferred embodiment of a present invention.

FIG. 45 is a section view taken along line 45-45 in FIG. 44.

FIG. 46 is a section view taken along line 46-46 in FIG. 44.

FIG. 47 is a section view taken along line 47-47 in FIG. 44.

FIG. 48 is a section view taken along line 48-48 in FIG. 44.

FIG. 49 is a section view taken along line 49-49 in FIG. 44.

FIG. 50 is a section view taken along line 50-50 in FIG. 44.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed description of the best presently knownmodes of carrying out the inventions. This description is not to betaken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the inventions.

The detailed description of the preferred embodiments is organized asfollows:

-   -   I. Introduction    -   II. Exemplary Lesion Formation Apparatus Capable of Being        Secured Around an Organ    -   III. Exemplary Clamp Based Lesion Formation Apparatus    -   IV. Exemplary Probe Based Lesion Formation Apparatus

The section titles and overall organization of the present detaileddescription are for the purpose of convenience only and are not intendedto limit the present inventions.

I. Introduction

This specification discloses a number of structures, mainly in thecontext of cardiac treatment, because the structures are well suited foruse with myocardial tissue. Nevertheless, it should be appreciated thatthe structures are applicable for use in therapies involving other typesof soft tissue. For example, various aspects of the present inventionshave applications in procedures concerning other regions of the bodysuch as the prostate, liver, brain, gall bladder, uterus, breasts,lungs, and other solid organs.

II. Exemplary Lesion Formation Apparatus Capable of Being Secured Aroundan Organ

A lesion formation apparatus 100 in accordance with a preferredembodiment of a present invention is illustrated in FIGS. 1-3. Theillustrated embodiment includes an inflatable cryogenic element 102carried on a base member 104 and a connector device 106 that may be usedto position the longitudinal ends of the inflatable cryogenic elementadjacent to one another. A fluid transmission space 108 is definedwithin the inflatable cryogenic element 102. The exemplary lesionformation apparatus 100 also includes an infusion lumen 110 and aventilation lumen 112 that extend a short distance into the longitudinalends of the inflatable cryogenic element 102. The infusion andventilation lumens 110 and 112, which are in communication with thefluid transmission space 108, are held in place with adhesive material114. The adhesive material 114 also seals the longitudinal ends of theinflatable cryogenic element 102. Each of these elements is discussed ingreater detail below.

As illustrated for example in FIG. 4, the lesion formation apparatus 100is connected to a cryogenic fluid supply and control apparatus 200 in asurgical system 10. The cryogenic fluid supply and control apparatus200, which may be used in combination with any of the other lesionformation apparatus described herein, includes housing 202, a fluidoutlet port 204, a fluid inlet port 206 and an electrical connector 208.The fluid outlet port 204 may be coupled to the infusion lumen 110 by atube 210, and the fluid inlet port 206 may be coupled to the ventilationlumen 112 by a tube 212. As discussed below with reference to FIGS.30-32, the electrical connector 208 may be used to connect the cryogenicfluid supply and control apparatus 200 to, for example, a connector thatis associated with temperature sensors and/or a valve, in thoseinstances where the apparatus includes the temperature sensors and/or avalve.

The lesion formation apparatus 100 may be positioned around portions oforgans during lesion formation procedures performed with the surgicalsystem 10. For example, one method of treating focal atrial fibrillationwith the lesion formation apparatus 100 involves the creation oftransmural lesions around the pulmonary veins. Lesions may be createdaround the pulmonary veins individually, in pairs, or, as is illustratedin FIG. 4A, a single transmural epicardial lesion L may be createdaround all four of the pulmonary veins PV. Such a lesion may be formedby positioning the lesion formation apparatus 100 around the pulmonaryveins PV in the manner illustrated in FIG. 4. The connector device 106may be used to secure the longitudinal ends of the inflatable cryogenicelement 102 in close proximity to one another. Although there is aslight space between the ends of the inflatable cryogenic element 102 inFIG. 4 in order to more clearly show various elements of the illustratedembodiment, the ends would typically be in contact with one another orslightly overlap in actual use. Cryogenic fluid from the cryogenic fluidsupply and control apparatus 200 is then passed through the inflatablecryogenic element 102, by way of the infusion and ventilation lumens 110and 112, to form the lesion.

The inflatable cryogenic element 102 illustrated in FIGS. 1-3 ispreferably formed from a thin tube 116. Referring more specifically toFIGS. 2 and 3, the tube 116 may be flattened against the base member 104and secured to the base member with adhesive 118. Flattening the tube116 and securing it to the base member 104 in this manner prevents thetube from buckling when pulled into a loop, increases the amount ofsurface area that will be in contact with tissue when the inflatablecryogenic element 102 is pressurized (or “inflated”), improves contactstability when the inflatable cryogenic element is pressurized, andminimizes folding and twisting of the cryogenic element when it isdeflated. Flattening the tube 116 and securing it to the base member 104in this manner also increases the strength of the bond between the tubeand the base member and minimized the profile (i.e. the height in theorientation illustrated in FIGS. 1-3) of the lesion formation apparatus100. Additionally, in those instances where the base member 104 isformed from insulating material (discussed below), this configurationinsures that about one-half of the inflatable cryogenic element 102 willbe thermally isolated from tissue.

The exemplary tube 116 is preferably formed from material that isrelatively high in thermal conductivity. A suitable temperature gradientacross the wall of the tube is about 2° C. or less. The tube materialshould also result in an inflatable cryogenic element 102 that has aburst pressure rating which exceeds the operating pressures within theinflatable cryogenic element. In the illustrated implementations forexample, and assuming that liquid perfluorocarbon will be supplied tothe inflatable cryogenic element 102 at a rate of 300 ml/min. and atemperature of minus 100° C., a suitable burst pressure rating would beabout 760 mm Hg (1 atmosphere). Another important consideration is tearresistance because the inflatable cryogenic element 102 will besubjected to forces that could result in tearing (and leaks) when thelesion formation apparatus 100 is deployed around a body structure. Forexample, the inflatable cryogenic element 102 will be subjected torelatively large tearing forces when deployed around the inferiorpulmonary veins in the posterior aspect to the heart. The presentinventors have determined that inflatable cryogenic elements with aburst pressure rating of about 3800 mm Hg (5 atmospheres) will not tearunder these conditions. Accordingly, a suitable burst pressure rating isabout 3800 mm Hg (5 atmospheres).

In one mode of operation, the inflatable cryogenic element 102 may besupplied with liquid cooling fluid in such a manner that, as the liquidcooling fluid flows through the inflatable cryogenic element, thepressure within the cryogenic element will be less than about 100 mm Hg,which results in a resilient cryogenic element. Such a resilientcryogenic element is softer and less traumatic to tissue than turgidcryogenic elements (i.e. those whose internal pressure is greater than100 mm Hg). It is also able to better conform to tissue. It should alsobe noted that there are a variety of ways to achieve the relatively lowpressures (i.e. less than 100 mm Hg) within the inflatable cryogenicelement 102. For example, configuring the infusion and ventilationlumens 110 and 112 such that the cross-sectional area of the infusionlumen is less than that of the ventilation lumen is one way to produce alow pressure within the inflatable cryogenic element 102.

Although the present inventions are not limited to any particularmaterials, suitable materials for the inflatable cryogenic element 102include biaxially oriented polyethylene terephthalate (PET), Nylon, andPebax® heat shrink tubing. The wall of such tubing will typically beabout 0.001 inch to 0.0005 inch thick. Conductive polymer mixtures (suchas 25% graphite filled Pebax® 2533), which allow for thicker walls whilemaintaining adequate levels of heat transfer, are other examples ofsuitable materials. Semi-compliant, compliant and elastomeric materialsmay also be employed. Here, thicknesses of about 0.004 inch to 0.008inch would be required to compensate for stretching.

In addition to supporting the inflatable cryogenic element 102, the basemember 104 in the illustrated embodiment functions as an insulationdevice to protect non-target tissue adjacent to the target tissue fromthe cryogenic element. The exemplary base member 104 is a flexibledevice that, as illustrated in FIGS. 2 and 3, is generally rectangularin cross-section. However, a wide variety of alternative configurationsare possible. Such configurations include, but are not limited to, theconfigurations illustrated in FIGS. 5-8. Referring first to FIG. 5, thebase member 104 a includes a groove 120 which receives a portion of thecryogenic element 102. Such a configuration provides a relatively lowprofile, reduces the possibility that the cryogenic element willseparate from the base member, provides additional lateral insulation,and reduces the likelihood that the cryogenic element will collapse. Theexemplary base member 104 b illustrated in FIG. 6 wraps around the sidesof the cryogenic element 102 in order to prevent the ablation of tissuethat is laterally adjacent to the target tissue. Alternatively, thesides of the base member may simply extend laterally beyond the sides ofthe cryogenic element 102. Turning to FIG. 7, the exemplary base member104 c is a composite formed from a number of layers of differentmaterials. Such composites can be configured for superior twistresistance or pre-shaped to aid the physician during the positioningprocess.

The exemplary base member 104 d illustrated in FIG. 8 includes aplurality of reinforcing members 122, such as straight or pre-shapedpolymer, composite or metal members, that prevent twisting of the lesionformation apparatus 100, hold a shaped lesion formation apparatusstraight for introduction, or provide lumens for temperature sensorwires or other elements. Alternatively, as illustrated in FIG. 8A, theexemplary base member 104 e simply includes a plurality of lumens 123.

Base members may also perform specific functions within a lesionformation apparatus. As illustrated for example in FIGS. 8B-8D, a basemember 104 f in the lesion formation apparatus 100 h includes apre-shaped reinforcing member 122 a (e.g. a thin strip of Nitinol) witha pre-shaped loop configuration and a removable stylet 122 b (e.g. asteel rod) that is straight and rigid enough to overcome the bendingforces applied by pre-shaped reinforcing member 122 a. The removablestylet 122 b is carried within a tube 122 c that defines alongitudinally extending lumen within the base member 104 f. Absent thepresence of the removable stylet 122 b, the base member 104 f, with itspre-shaped reinforcing member 122 a, will bend the lesion formationapparatus 100 h into a loop and will maintain the loop during lesionformation procedures.

In the illustrated embodiment, the longitudinal ends of the cryogenicelement 102 overlap slightly in order to insure that the lesion formedthereby will be a complete circle. Alternatively, pre-shaped reinforcingmember 122 a may be configured such that the longitudinal ends abut oneanother, or such that there is a gap between the longitudinal ends, ifthe intended application so requires. Additionally, although theillustrated reinforcing member has a substantially circular shape, anyshape suitable for the intended application may be employed. Finally, apre-shaped reinforcing member and stylet may be incorporated into any ofthe lesion formation apparatus described herein with reference to FIGS.1-32.

During use, the removable stylet 122 b will be in place within the tube122 c prior to deployment of the associated lesion formation apparatus.The removable stylet 122 b will be withdrawn in the direction of arrow Aas the apparatus is advanced in a direction tangential to the targettissue structure, thereby allowing the pre-shaped reinforcing member 122a to bend the apparatus into a loop shape around the target structure.The stylet 122 b is preferably slightly longer than the base member 104f is order to provide a free end that may be grasped by the physician.The stylet 122 b may, in some instances, have a slight curvature whereapplications so require.

In addition to bending the lesion formation apparatus 100 h into thebent orientation illustrated in FIG. 8D, the pre-shaped reinforcingmember 122 a will maintain the lesion formation apparatus in the bentorientation during lesion formation procedures. As such, the connectordevice 106 need not be used (although it may be used if desired) tomaintain the lesion formation apparatus in the loop orientation. The endportions 126 and 128 may still be used, however, to pull the lesionformation apparatus around a tissue structure as it is being positionedfor a procedure.

In other alternative base member configurations, the cross-sectionalshape (in the orientation illustrated in FIGS. 5-8) may be varied. Forexample, instead of the rectangular cross-sectional shape illustrated inFIGS. 1-3, the cross-sectional base members may be thicker, thinner,circular, semi-circular, triangular, or any other shape that is suitablefor the intended use. Base members in accordance with the presentinventions may also be hollow (e.g. molded hollow bodies) or have aplurality of small channels formed therein.

Although the present inventions are not limited to any particularmaterials, suitable materials for the base members 104-104 d includeflexible polymer (elastomer) open and closed cell foams. In thoseinstance where open cell foams are used, the base member may include asealing skin (not shown) to prevent fluid absorption. Flexiblethermoplastics and thermoset polymers may also be employed. The basemembers are also preferably insulating and, in some instances, transferheat at a rate of 0.33 w/cm² of exposed surface area, which is lowenough to prevent freezing. A typical thermal conductivity for aninsulator is less than about 0.002 w/cm-K. Foams having a thickness ofabout 2 mm will provide this level of insulation, as will thin (e.g. 0.8mm) balloons filed with a gas such as CO₂. In addition to protectingadjacent tissue from the extremely lower temperatures associated withthe inflatable cryogenic element 102, an insulating base member makesthe lesion formation apparatus “one directional” in that heat transferto the cryogenic element will take place on the surface opposite thebase member. Such an arrangement is more efficient that one in which theheat transfer can take place along the entire perimeter of the cryogenicelement 102.

As illustrated in FIGS. 1-4, the exemplary connector device 106 is arelatively thin, flexible elongate device that includes a main portion124 and a pair of end portions 126 and 128. The main portion 124 issecured to the base member 104, preferably along the entire length ofthe base member. The end portions 126 and 128, which extend from thelongitudinal ends of base member 104, may be used to pull the lesionformation apparatus 100 into the orientation illustrated in FIG. 4 andthen tied onto a knot 130 to hold the lesion formation apparatus inplace. The end portions 126 and 128 may also be provided with knots,beads, eyelets and/or any other closure mechanism that can be used tohold the end portions (as well as the longitudinal ends of theinflatable cryogenic element 102 and base member 104) in the orientationillustrated in FIG. 4. It should be noted that the connector device 106is preferably, although not necessarily, secured to the side of the basemember 104 opposite the inflatable cryogenic element 102, as opposed toin between the base member and cryogenic element. Such an arrangementisolates the cryogenic element 102 from the pulling stresses associatedwith the introduction, positioning and securing of the lesion formationapparatus 100.

Although the present inventions are not limited to any particularmaterials, one suitable material for the connector device 106 is thin(e.g. about 0.005 inch to 0.025 inch) woven fabric ribbon. This materialis relatively soft and will not slice through tissue during use. Othersuitable materials include polymer films and cords. The main portion 124may be secured to the base member 104 with a flexible adhesive (notshown) such as polyurethane or a Polycin® and Vorite® mixture.

The exemplary infusion and ventilation lumens 110 and 112 (FIGS. 1 and3) will typically extend about 3 mm to 10 mm into the respectivelongitudinal ends of the inflatable cryogenic element 102 and areprovided with polycarbonate Luer connectors 132 and 134 that may be usedto connect the infusion and ventilation lumens to a source of cryogenicfluid by way of, for example, the tubes 210 and 212 (FIG. 4). Dependingon the type of cryogenic cooling that is desired, the infusion andventilation lumens may be used to supply and ventilate super-cooledfluid, such as liquid perfluorocarbon that has been cooled to a suitablylow temperature such as minus 100° C., or to supply liquid nitrous oxideand ventilate the gas that results from the expansion within theinflatable cryogenic element 102. Other suitable connectors includestopcocks, valves, check valves, T or Y-fittings adapted forpurging/flushing or temperature monitoring. In order to withstand theextremely cold temperatures associated with cryogenic cooling, theinfusion and ventilation lumens 110 and 112 are preferably formed frommaterials such as Tygon®, C-Flex®, or a polyurethane polymer. Theinfusion and ventilation lumens 110 and 112 may also be insulated forimproved performance and safety.

As noted above, adhesive material 114 (FIG. 3) may be used to secure theinfusion and ventilation lumens 110 and 112 in place, as well as to sealthe longitudinal ends of the inflatable cryogenic element 102. Suitableadhesives include flexible UV activated adhesives such as Loctite® 321and 3021. Alternatively, the infusion and ventilation lumens 110 and 112may be secured in place and the ends of the inflatable cryogenic element102 sealed by heat curing or RTV polyurethane. The adhesive 118 ispreferably a Vorite® and polycin polyurethane blend.

The overall dimensions of lesion formation apparatus in accordance withthe present inventions will, of course, depend on the intendedapplication. In one exemplary implementation that is suitable forforming epicardial lesions around the pulmonary veins, the inflatablecryogenic element 102 is about 15 cm to 30 cm in length. The aspectratio, i.e. the width to thickness (or height) ratio, is about 2-3 to 1.Typically, in the orientation illustrated in FIG. 3, the widthinflatable cryogenic element 102 is about 4 mm to 12 mm and thethickness is about 1 mm to 4 mm, when secured to the base member 104 inthe manner illustrated in FIG. 3. The length and width of the basemember 104 corresponds to that of the cryogenic element 102 in theexemplary implementation, i.e. the base member is about 15 cm to 30 cmin length and about 4 mm to 12 mm wide. The thickness, which depends onthe materials, will typically be about 1 mm to 7 mm. With respect to theexemplary connector device 106, the width will correspond to that of thebase member 104 and, accordingly, is about 4 mm to 12 mm. The endportions 126 and 128 extend about 15 cm to 60 cm from the longitudinalends of the cryogenic element.

Another exemplary lesion formation apparatus is generally represented byreference numeral 100 a in FIGS. 9-12. The lesion formation apparatus100 a is substantially similar to the lesion formation apparatus 100described above with reference to FIGS. 1-8 and similar elements arerepresented by similar reference numerals. Here, however, the inflatablecryogenic element 102 a includes a support structure 136. A variety ofdifferent support structures may be employed. In the illustratedembodiment, for example, the support structure is a spiral coil extendsfrom a point slightly inside one longitudinal end of the inflatablecryogenic element 102 a (i.e. about 1 mm to 4 mm) to a point slightlyinside the other longitudinal end. The support structure 136, whichincludes short, linear longitudinal end portions 138 that are held inplace by the adhesive 114, may be formed from a thin wire, such as aNitinol wire that is about 0.016 inch in diameter. The overall diameterof the support structure 136 itself will depend on the intendedapplication. In epicardial applications such as that illustrated in FIG.4, the diameter will typically be about 2 mm to 4 mm. Aluminum,stainless steel, copper or silver wires may also be used in order toimprove heat transfer from the tissue to the fluid. Thin layers ofadhesive 114 are also deposited within the lateral edges of the tube 116in order to prevent draping or bagging.

There are a number of advantages associated with the use of a supportstructure such as the support structure 136. For example, the supportstructure insures that the fluid transmission space 108 will have asubstantially constant cross-sectional area. A coil-type supportstructure (e.g. the support structure 136) will also create secondaryflow within the transmission space, which increases thermal efficiency.Coil-type support structures also create ridges that may help theassociated lesion formation apparatus engage soft or fatty substratesfor thermal transmission, provide anchoring stability and increasecontact surface area.

Another exemplary lesion formation apparatus is generally represented byreference numeral 100 b in FIGS. 13-16. The lesion formation apparatus100 b is substantially similar to the lesion formation apparatus 100 adescribed above with reference to FIGS. 9-12 and similar elements arerepresented by similar reference numerals. Here, however, the inflatablecryogenic element 102 b has a relatively non-compliant inner region anda relatively compliant outer region. The relatively compliant outerregion allows the lesion formation apparatus 100 b to conform to tissue,thereby insuring good tissue contact, and also acts a barrier in theevent of any leakage from the inner region.

In the exemplary implementation illustrated in FIGS. 13-16, the outerregion of the inflatable cryogenic element 102 b includes an outer fluidtransmission space 109 that is defined by a thin outer tube 117, whilethe inner region includes an inner fluid transmission space 108 that isdefined by a thin inner tube 116 b located within the outer tube. Theouter fluid transmission space 109 is connected to a source of thermallyconductive media by infusion and ventilation lumens 111 and 113, and theinner fluid transmission space 108 is connected to a source of cryogenicfluid by the infusion and ventilation lumens 110 and 112. The shape ofthe inner fluid transmission space 108 is generally maintained by thesupport structure 136, which also prevents the outer tube 117 fromoccluding the inner tube 116 b.

The outer tube 117 is preferably formed from thin (e.g. about 0.002inch), compliant (or elastomeric) and thermally conductive material suchas unrecovered PET or polyurethane rubber. The longitudinal ends of theouter tube 117 are sealed around the inner tube 116 b and the infusionand ventilation lumens 111 and 113 with adhesive 114. The outer tube 116b is flattened against the base member 104 and secured to the basemember with adhesive 118. The inner tube 116 b may be formed from arelatively non-complaint material, such as recovered PET, that is heatshrunk onto the support structure 136. Adhesive 114 is also used to sealthe longitudinal ends of the inner tube 116 b around the infusion andventilation lumens 110 and 112. Stopcocks 133 and 133 are provided onthe inlet lumens 110 and 111, and stopcocks 135 and 135 are provided onthe outlet lumens 112 and 113. The stopcocks may be used to exclude airbubbles from purged, filled spaces and to prevent fluid leakage duringremoval of the apparatus from the patient and to maintain the inflatedgeometry after the cryogenic supply and control apparatus 200 hasstopped supplying fluid. It should also be noted that stopcocks 133 and135 may be used in place of the Luer connectors 132 and 134 in the otherembodiments disclosed herein.

Prior to use, the outer fluid transmission space 109 will be purged ofair. After the lesion formation apparatus 100 b is positioned adjacentto the target tissue (e.g. in the manner illustrated in FIG. 4), thefluid transmission space 109 will be filled with a thermally conductivemedia such as water. Cryogenic fluid is then directed through the innerfluid transmission space 108. In those instances where the outer fluidtransmission space is filled with water, the water will typically turnto ice. Heat is then transferred from the tissue, through the outer tube117, the conductive media therein, and the inner tube 116 b to thecryogenic fluid.

Another exemplary lesion formation apparatus is generally represented byreference numeral 100 c in FIGS. 17-20. The lesion formation apparatus100 c is substantially similar to the lesion formation apparatus 100described above with reference to FIGS. 1-8 and similar elements arerepresented by similar reference numerals. Here, however, the infusionand ventilation lumens 110 and 112 extend from the same longitudinal endof the lesion formation apparatus. The inlet lumen 110 extends a shortdistance into the inflatable cryogenic element 102 and is held in placewith adhesive material 114. The adhesive material 114 also seals thatlongitudinal end of the inflatable cryogenic element 102. A portion ofthe outlet lumen 112 extends under the cryogenic element 102 to a pointbeyond the other longitudinal end of the cryogenic element. An end cap140, which is associated with the other end of the cryogenic element102, transfers the cryogenic fluid from the cryogenic element to theoutlet lumen 112.

In the exemplary implementation illustrated in FIGS. 17-20, a shortconnector lumen 112 c extends from the end of the inflatable cryogenicelement into the end cap 140. The lumen 112 c is held in place withadhesive material 114, which also seals that longitudinal end of theinflatable cryogenic element 102. The end cap 140 includes a baseportion 142 and a cover 144 that define an inner region 146 which isopen at both ends. The end cap may, alternatively, be a one piecedesign. The connector lumen 112 c and outlet lumen 112 extend into oneend of the inner region 146, which is sealed with the adhesive 114. Theother end of the inner region 146 is also sealed with adhesive 114.Cryogenic fluid that exits the cryogenic element 102 by way of theconnector lumen 112 c flows though a space 150 within the end cap 140(i.e. the portion of the inner region 146 between the adhesive material)and into the outlet lumen 112. The cryogenic fluid then passes under thecryogenic element 102 on its way out of the lesion formation apparatus100 c.

It should be noted that the concept of placing infusion and ventilationlumens at one end of an inflatable cryogenic element, and an end cap (orend caps) at the other end, is also applicable to the exemplaryapparatus 100 a illustrated in FIGS. 9-12 and the exemplary apparatus100 b illustrated in FIGS. 13-16.

As illustrated above, the configurations of the inflatable cryogenicelement and base member are susceptible to a wide degree of variation.There are also a number of alternative connector configurations. Turningto FIGS. 21-24, the exemplary lesion formation apparatus 100 d issubstantially similar to the lesion formation apparatus 100 describedabove with reference to FIGS. 1-8 and similar elements are representedby similar reference numerals. Here, however, the lesion formationapparatus 100 d includes a fastener 148 that may be used instead of, orin addition to, the connector device 106 when fixing the position of theapparatus around an organ.

In the exemplary implementation illustrated in FIGS. 21-24, the fastener148 includes a pair of fastening elements 150 and 152 that areassociated with the longitudinal ends of the inflatable cryogenicelement 102. The exemplary fastening elements 150 and 152 are hook andloop fastener strips, such as Velcro® strips. Fastening element 150 iscarried on the bottom of the connector device main portion 124 and facesdownwardly (in the orientation illustrated in FIG. 21), while thefastening element 152 is carried by a support 154 that is secured to theconnector device main portion and faces upwardly. So arranged, thefastening elements 150 and 152 will face one another, thereby allowingthem to be connected to one another, when the lesion formation apparatus100 d is bent into a loop in the manner illustrated in FIG. 24.

Other exemplary fastening elements include devices that will hold theconnector device end portions 126 and 128, such as clamps andspring-biased locks. In those instances where the end portions 126 and128 include knots, cleats (i.e. a tube with slots that receive theknots) may be employed.

The exemplary fastener 148 may also be used in combination with thelesion formation apparatus 100 a illustrated in FIGS. 9-12, theexemplary lesion formation apparatus 100 b illustrated in FIGS. 13-16,and the exemplary lesion formation apparatus 100 c illustrated in FIGS.17-20.

Another exemplary lesion formation apparatus is generally represented byreference numeral 100 e in FIGS. 25 and 26. The lesion formationapparatus 100 e is substantially similar to the lesion formationapparatus 100 described above with reference to FIGS. 1-8 and similarelements are represented by similar reference numerals. Here, however,the connector device 106 e includes a pair of flexible pull strings 124e and 125 e and a pair of flexible end strings 126 e and 128 e. The pullstrings 124 e and 125 e are secured to the base member 104, andpreferably along the entire length of the base member, with adhesive118. The longitudinal ends of the pull strings 124 e and 125 e aresecured to one another, and to the end strings 126 e and 128 e, by knots127 e (or other fastening methods). The connector device 106 e may alsobe used in place of the connector device 106 in the lesion formationapparatus 100 a-d illustrated in FIGS. 9-24.

The exemplary lesion formation apparatus illustrated in FIGS. 1-26 mayalso be configured in a manner that will help the physician distinguishvarious elements from one another. For example, the lesion formationapparatus 100 f illustrated in FIG. 27, which is essentially identicalto the apparatus 100 described above with reference to FIGS. 1-8,includes a connector device 106 f that is relatively dark in color,while the inflatable cryogenic element 102 is relatively light in color.This may also be reversed, with the cryogenic element 102 formed from arelatively dark material and the connector device 106 f formed from arelatively light material. The color of the base member 104 may also beselected so as to help the physician identify various apparatus elementsduring surgical procedures. Stripes and other patterns may also beemployed. A visible scale may also be provided on the cryogenic element,the base member or the connector device in order to allow the physicianto monitor and manage the full length of the apparatus during theprocedure.

The exemplary lesion formation apparatus illustrated in FIGS. 1-27 mayalso be provided with a movable insulation device that prevents some ofthe tissue that would otherwise be ablated by the inflatable cryogenicelement from being ablated. As illustrated for example in FIGS. 28 and29, a slidable insulation sleeve 156 is positioned around a portion ofthe lesion formation apparatus 100. The length of the insulation sleeve156 will vary from application to application, but will typically belonger that the cryogenic element 102 itself and up to twice the lengthof the cryogenic element. This allows the insulation sleeve 156 toprovide an insulative barrier between the lesion formation apparatus 100and the patient, from the exterior of the body to the target tissueregion. Suitable materials include polyurethane or silicone, and lumens157 may be provided to increase the insulative capability of the sleeve.The insulation sleeve 156 may, for example, be used to cover themajority of the cryogenic element 102 during touch up procedures to fillin gaps in lesions. Here, the insulation sleeve 156 may be pulledproximally until the desired length of the cryogenic element 102 isexposed.

In an alternative configuration, which is illustrated in FIGS. 29A and29B, the exemplary insulation sleeve 156 a includes a window 159 thatallows small lesions to be formed in specific locations. Sleeve 156 a isalso configured to prevent the lesion formation apparatus 100 fromrotating and to insure that the inflatable cryogenic element 102 isaligned with the window 159. More specifically, the internal lumen ofthe insulation sleeve 156 a is substantially D-shaped and the flatportion of the “D” is adjacent to the base member 104.

The exemplary lesion formation apparatus illustrated in FIGS. 1-29B mayalso be provided with one or more temperature sensors, such asthermocouples or thermistors, so that tissue temperature can bemonitored during lesion formation procedures. Referring to FIGS. 30 and31, the exemplary lesion formation apparatus 100 g, which issubstantially similar to the lesion formation apparatus 100 describedabove with reference to FIGS. 1-8, is provided with a plurality oftemperature sensors 158. The temperature sensors 158 may be equallyspaced along the length of the inflatable cryogenic element 102. In oneexemplary implementation where the cryogenic element is 30 cm in length,the temperature sensors 158 are positioned such that adjacenttemperature sensors are 5 cm apart and the two temperature sensorsclosest to the longitudinal ends of the cryogenic element are 5 cm fromthe longitudinal ends. The temperature sensors 158 may be secured to theinflatable cryogenic element 102 near the base member 104 with, forexample, flexible UV activated adhesive 160.

Each temperature sensor 158 is connected to a signal wire 162 thattransmits temperature information from the temperature sensors to, forexample, the cryogenic fluid supply and control apparatus 200 (FIG. 4).The signal wires are secured to the inflatable cryogenic element 102near the temperature sensors 158 with quick curing adhesive 164, such ascyanoacrylate, and are routed through a small diameter flexible polymertube 165. The tube 165 is attached to the base member 104 adjacent tothe inflatable cryogenic element 102. In the exemplary implementationillustrated in FIGS. 30 and 31, the signal wires 162 pass from the smalldiameter tube 165 and into a more robust tube (or cable) 166 at one endof the apparatus, and are then connected to an electrical connector 168.The connector 168 may, in turn, be connected to the cryogenic fluidsupply and control apparatus 200.

The temperature sensor locations are not limited to those illustrated inFIGS. 30 and 31. For example, temperature sensors may be placed on bothsides of the inflatable cryogenic element 102. Temperature sensors may,alternatively or in addition, also be placed along the top of thecryogenic element 102.

The exemplary lesion formation apparatus illustrated in FIGS. 1-29 mayalso be configured in such a manner that the number of uses is limited.Referring to FIG. 30, a valve 170 may be placed within an inflatablecryogenic element (e.g. the cryogenic element 102) that will, whenclosed, prevent the flow of cryogenic fluid from the fluid transmissionspace 108 to the ventilation lumen 112. Suitable valves include, but arenot limited to, normally closed electronic-operating valves and normallyclosed solenoid valves. The valve 170 may be connected to the connector168 for control purposes (as shown) or have its own connector. Theexemplary valve 170 also includes a battery and a timer circuit (notshown).

Regardless of the type of valve used, the valve 170 will be opened thefirst time that the connector 168 is connected to the cryogenic fluidsupply and control apparatus 200. When connected, the valve will open,battery will be charged and the timer circuit will begin tracking time.After a predetermined period (e.g. 24 hrs.), the valve 170 will closepermanently, thereby preventing further use.

It should be noted that the exemplary valve 170 need not be locatedwithin the inflatable cryogenic element. As illustrated in FIG. 32, forexample, the valve 170 may be located along a portion of the ventilationlumen 112. Alternatively, the valve may be located along a portion ofthe inlet lumen 110.

Ill. Exemplary Clamp Based Lesion Formation Apparatus

As illustrated for example in FIG. 33, an exemplary surgical system 20in accordance with one embodiment of a present invention includes thecryogenic fluid supply and control apparatus 200 and a cryogenic clampapparatus 300. The cryogenic clamp apparatus 300 includes a clamp and atissue coagulation assembly that may be secured to the clamp. As usedherein, the term “clamp” includes, but is not limited to, clamps, clips,forceps, hemostats, and any other surgical device that includes a pairof opposable clamp members that hold tissue, at least one of which ismovable relative to the other. In some instances, the clamp members areconnected to a scissors-like arrangement including a pair of handlesupporting arms that are pivotably connected to one another. The clampmembers are secured to one end of the arms and the handles are securedto the other end. Certain clamps that are particularly useful inminimally invasive procedures also include a pair of handles and a pairof clamp members. Here, however, the clamp members and handles are notmounted on the opposite ends of the same arm. Instead, the handles arecarried by one end of an elongate housing and the clamp members arecarried by the other. A suitable mechanical linkage located within thehousing causes the clamp members to move relative to one another inresponse to movement of the handles. The clamp members may be linear orhave a predefined curvature that is optimized for a particular surgicalprocedure or portion thereof. The clamp members may also be rigid ormalleable.

One example of a clamp that may be employed in the cryogenic clampapparatus 300 is generally represented by reference numeral 302 in FIGS.33 and 41-43. Referring more specifically to FIGS. 41-43, the clamp 302includes a pair of rigid arms 304 and 306 that are pivotably connectedto one another by a pin 308. The proximal ends of the arms 304 and 306are respectively connected to a pair handle members 310 and 312, whilethe distal ends are respectively connected to a pair of clamp members314 and 316. The clamp members 314 and 316 may be rigid or malleableand, if rigid, may be linear or have a pre-shaped curvature. A lockingdevice 318 locks the clamp in the closed orientation, and prevents theclamp members 314 and 316 from coming any closer to one another than isillustrated in FIG. 41, thereby defining a predetermined spacing betweenthe clamp members. The clamp 302 is also configured for use with a pairof soft, deformable inserts (not shown) that may be removably carried bythe clamp members 314 and 316 and allow the clamp to firmly grip abodily structure without damaging the structure. To that end, the clampmembers 314 and 316 each include a slot 320 (FIGS. 42 and 43) that isprovided with a sloped inlet area 322 and the inserts include matingstructures that are removably friction fit within the slots. Theexemplary tissue coagulation assembly 324 (FIG. 33 and 34) may bemounted on the clamp members in place of the inserts.

As illustrated in FIGS. 33-37, the exemplary tissue coagulation assembly324, includes an inflatable cryogenic element 326 and a series oftemperature sensors 328, such as thermocouples or thermistors. Theinflatable cryogenic element 326 and temperature sensors 328 arerespectively carried on support structures 330 and 332, which areconnected to a tubular member 334 by a connector 336. The tubular member334 is secured to a handle 335. The inflatable cryogenic element 326 maybe connected to a source of cryogenic fluid, such as the cryogenic fluidsupply and control apparatus 200 and, to that end, the support structure330 includes an infusion lumen 338 and a ventilation lumen 340. Thetemperature sensors 328 are connected to signal wires 342 which passthrough a signal wire lumen 344 in the support structure 332. Thetubular member 334 includes infusion and ventilation lumens 346 and 348and a signal wire lumen 350, which are respectively connected to theinfusion and ventilation lumens 338 and 340 in the support structure330, and the signal wire lumen 344 in the support structure 332, by theconnector 336.

The exemplary tissue coagulation assembly 324 also includes a pair ofessentially identical base members 352 which are used to connect theassembly to the clamp 502. Although the configuration of the tissuecoagulation assembly may vary from application to application to suitparticular situations, the exemplary tissue coagulation assembly 324 isconfigured such that the inflatable cryogenic element 326 and thetemperature sensors 328 will be parallel to one another as well asrelatively close to one another (i.e. a spacing of about 1-10 mm) whenthe clamp 502 is in the closed orientation. Such an arrangement willallow the tissue coagulation assembly to firmly grip a bodily structurewithout cutting through the structure. Referring more specifically toFIGS. 38-40A, the illustrated base members 352 include a main portion354, with a groove 356 that is configured to receive the supportstructure 330 (or 332), and a connector 358 that is configured toremovably mate with the slot 320 in the clamp 302. The configuration ofthe groove 356 allows the support structure 330 (or 332) to be snap fitinto the base member 352. Adhesive may also be used within the groove356 to insure that the inflatable cryogenic element 326 and supportstructure 332 do not separate from the base members 352. The exemplaryconnector 358 is provided with a relatively thin portion 360 and arelatively wide portion 362, which may consist of a plurality of spacedmembers (as shown) or an elongate unitary structure, in order tocorrespond to the shape of the slot 320 in the clamp 302.

The exemplary inflatable cryogenic element 326 is formed from a thin,flexible tube 364 (FIGS. 39 and 40) that is positioned around thesupport structure 330. A small portion of the tube 364 is wedged betweenthe outer surface of the support structure 330 and the groove 356 in thebase member 352, while the remainder of the tube bulges out and, wheninflated, defines the fluid transmission space 366. To that end, thesupport structure 330 includes an infusion aperture 368 that connectsthe infusion lumen 338 to the fluid transmission space 366, and aventilation aperture 370 that connects the fluid transmission space tothe ventilation lumen 340. The infusion aperture 368 is preferably(although not necessarily) located near the distal end of the inflatablecryogenic element 326 and the ventilation aperture 370 is located nearthe proximal end. The longitudinal ends of the tube 364 are sealedaround the support structure 330 with adhesive 371 (FIG. 40A). Suitableadhesives include UV activated adhesives and cyanoacrylate.

The exemplary inflatable cryogenic element 326 is preferably wider thanit is tall in order to increase the surface area that will be in contactwith tissue during use. In the exemplary implementation illustrated inFIGS. 38-40, the portion of the tube 364 that is above the base member352 is generally elliptical in shape, thereby defining a generallyelliptical inflatable cryogenic element 326 (note the cross-sectionalshape illustrated in FIGS. 39 and 40). The major axis (i.e. width) tominor axis (i.e. height) ratio is about 2 to 1 in the exemplaryembodiment, e.g. a major axis of about 4 mm and a minor axis of about 2mm in epicardial applications. Of course, the cross-section shape may bevaried from application to application. The length of the inflatablecryogenic element 326 will also vary from application to application andmay be about 5 cm to 8 cm in epicardial applications.

With respect to materials, the inflatable cryogenic element 326 ispreferably formed from the same materials as the inflatable cryogenicelement 102. However, because the inflatable cryogenic element 326 isbeing used in combination with a clamp, it will not be subjected to thesame shear (or “tearing”) stresses that the inflatable cryogenic element102. As a result, the inflatable cryogenic element 326 may be configuredwith a lower burst pressure rating, e.g. about 760 mm Hg (1 atmosphere),which allows the material to be of lower ultimate strength. As theliquid cooling fluid flows through the inflatable cryogenic element 326,the pressure within the inflatable cryogenic element will typically beless than about 100 mm Hg, which results in a resilient cryogenicelement. Such a resilient cryogenic element is softer and less traumaticto tissue than turgid cryogenic elements (i.e. those whose internalpressure is greater than 100 mm Hg). It is also able to better conformto tissue. Conventional cryogenic elements that employ the JT effectoperate with internal gas pressures on the order of 700 mm Hg and arequite turgid.

It should be noted here that there are a variety of ways to achieve therelatively low pressures (i.e. less than 100 mm Hg) within theinflatable cryogenic element 326. For example, the support structure 330may be configured such that the cross-sectional area of the infusionlumen 338 is less than that of the ventilation lumen 340.

Turning to the material used to form the other elements, the supportstructures 330 and 332 and tubular member 334 may be formed from PET orpolyurethane tubing. The base members 352 may be formed frompolyurethane, nylon, Pebax®, silicone, ceramics or metals such asaluminum, copper, stainless steel and Nitinol.

Referring to FIG. 33, the tissue coagulation assembly 324 may beconnected to, for example, the cryogenic fluid supply and controlapparatus 200 by way of fluid inlet and outlet tubes 372 and 374. Thefluid inlet and outlet tubes 372 and 374, which extend through thehandle 335 and are connected to the infusion and ventilation lumens 346and 348 in the tubular member 334, may be connected to the fluid ports204 and 206 on the cryogenic fluid supply and control apparatus 200. Thesignal wires 342 also extend through the handle 335 and terminate at anelectrical connector 376. A cable 214, with electrical connectors 216and 218, may be used to electrically connect the temperature sensors onthe tissue coagulation assembly 324 to the electrical connector 208 onthe cryogenic fluid supply and control apparatus 200.

The exemplary cryogenic clamp apparatus 300 may be reconfigured in avariety of ways. By way of example, but not limitation, one alternativetissue coagulation assembly includes a pair of the inflatable cryogenicelements 326. Each of the support structures carry an inflatablecryogenic element 326 and are configured in a manner similar to thesupport structure 330. Here, temperature sensors may be provided on oneor both of the inflatable cryogenic elements 326. The tissue coagulationassembly 324 may also be provided with apparatus, such as the valve 170illustrated in FIG. 30, to prevent multiple uses. Additionally, shouldapplications so require, any of the features of the inflatable cryogenicelements discussed in Section II (e.g. the support structure 136 or theouter fluid transmission space 109) may be incorporated into theinflatable cryogenic elements 326.

The exemplary cryogenic clamp apparatus 300 may be used to form lesionsin the following manner. The clamp members 314 and 316 may be positionedsuch that the inflatable cryogenic element 326 (in a deflated state) andthe temperature sensors 328 are on opposite sides of a tissue structure.For example, the inflatable cryogenic element 326 and temperaturesensors 328 may be positioned on opposites side of a single pulmonaryvein or a pair of pulmonary veins. The clamp members 314 and 316 maythen be brought into a completely closed orientation or, depending onthe tissue structure, a slightly open orientation so long as the tissuestructure is firmly held. Cryogenic liquid is then pumped from thecryogenic fluid supply and control apparatus 200 into the inflatablecryogenic element 326, thereby inflating the cryogenic element andcooling the target tissue. The temperature sensors 328 monitor thetissue temperature on the side of the target tissue structure oppositethe inflatable cryogenic element 326.

The inventors herein have determine that temperature on the side of thetarget tissue structure opposite the inflatable cryogenic element 326 isindicative of lesion transmurality (i.e. whether or not a lesion thatextends from one side of the target tissue structure to the other hasbeen formed). More specifically, the inventors herein have determinedthat measured temperatures of about minus 20° C. to about minus 40° C.on the side of the tissue structure opposite the side that is in contactwith the inflatable cryogenic element 326 are indicative of theformation of a transmural lesion. The cryogenic fluid supply and controlapparatus 200 may, therefore, be configured to discontinue the flow ofcryogenic liquid to the inflatable cryogenic element 326 when apredetermined temperature (e.g. a temperature between about minus 20° C.and about minus 40° C.) is measured by the temperature sensors 328.Alternatively, or in addition, the cryogenic fluid supply and controlapparatus 200 may also be configured to provide an audible or visibleindication that the predetermined temperature has been measured.

IV. Exemplary Probe Based Lesion Formation Apparatus

As illustrated for example in FIG. 44, an exemplary surgical system 30in accordance with one embodiment of a present invention includes thecryogenic fluid supply and control apparatus 200 and a cryogenicsurgical probe 400. Referring to FIGS. 44-50, the exemplary surgicalprobe 400 includes a relatively short shaft 402 and an inflatablecryogenic element 404 carried on the distal portion 406 of the shaft.The proximal portion 408 of the shaft 402 is secured to a handle 410. Astrain relief element 412 is also provided. The shaft 402 will typicallybe about 3 cm to about 12 cm in length and will also typically berelatively stiff. In other words, the shaft is either rigid, malleable,or somewhat flexible. A rigid shaft cannot be bent. A malleable shaft isa shaft that can be readily bent by the physician to a desired shape,without springing back when released, so that it will remain in thatshape during the surgical procedure. Thus, the stiffness of a malleableshaft must be low enough to allow the shaft to be bent, but high enoughto resist bending when the forces associated with a surgical procedureare applied to the shaft. A somewhat flexible shaft will bend and springback when released. However, the force required to bend the shaft mustbe substantial. The proximal portion 408 of the exemplary shaft 402(FIG. 45) is malleable and consists of a malleable hypotube 414 with anouter polymer jacket 416. The distal portion 406 of the exemplary shaft402 (FIG. 46) is malleable and consists of a malleable mandrel 418 and asupport structure 420. The proximal end of the mandrel 418 is secured tothe inner surface of the distal end of the hypotube 414 and the distalend of the mandrel is secured to a tip member 422. The tip member 422is, in turn, secured to the distal end of the support structure 420through the use of adhesive or other suitable instrumentalities.

As illustrated for example in FIGS. 44-46, the exemplary supportstructure 420 is a multi-lumen structure that includes an infusion lumen424, a ventilation lumen 426, a signal wire lumen 428 and a center lumen430 for the malleable mandrel 418. The distal ends of the infusion,ventilation, and signal wire lumens 424-428 are sealed by the tip member422 and associated adhesive. The infusion and ventilation lumens 424 and426 are respectively connected to infusion and ventilation tubes 432 and434, which extend through the shaft proximal portion 408 and the handle410 and may be connected to the fluid outlet and inlet ports 204 and 206on the cryogenic fluid supply and control apparatus 200.

Referring to FIGS. 46-48, the exemplary inflatable cryogenic element 404is formed from thin, flexible tube 436 that is positioned around thesupport structure 420. The proximal and distal ends of the tube 436 aresecured to the support structure 420 with adhesive 438, such as UVactivated adhesives or cyanoacrylate. When inflated, the inflatablecryogenic element 404 defines a fluid transmission space 440 between theinner surface of the tube 436 and the outer surface of the supportstructure 420. The adhesive 438 also seals the ends of the fluidtransmission space 440. Additionally, the support structure 420 includesan infusion aperture 442 that connects the infusion lumen 424 to thefluid transmission space 440, and a ventilation aperture 444 thatconnects the fluid transmission space to the ventilation lumen 426. Theinfusion aperture 442 is preferably (although not necessarily) locatednear the distal end of the inflatable cryogenic element 404 and theventilation aperture 444 is located near the proximal end.

With respect to materials and dimensions, the inflatable cryogenicelement 404 is preferably formed from the same materials as theinflatable cryogenic element 102. However, because the inflatablecryogenic element 404 is being used in combination with a surgicalprobe, it will not be subjected to the same shear (or “tearing”)stresses that the inflatable cryogenic element 102. As a result, theinflatable cryogenic element 404 may be configured with a lower burstpressure rating, e.g. about 760 mm Hg (1 atmosphere), which allows thematerial to be of lower ultimate strength. As the liquid cooling fluidflows through the inflatable cryogenic element 404, the pressure withinthe inflatable cryogenic element will typically be less than about 100mm Hg, which results in a resilient cryogenic element. Such a resilientcryogenic element is softer and less traumatic to tissue than turgidcryogenic elements (i.e. those whose internal pressure is greater than100 mm Hg). It is also able to better conform to tissue. The outerdiameter of the cryogenic element 404 is about 4 mm to 6 mm inepicardial applications, while the length of the cryogenic element isabout 3 cm to 12 cm and the outer diameter of the support structure 420is about 2 mm to 3 mm.

It should be noted here that there are a variety of ways to achieve therelatively low pressures (i.e. less than 100 mm Hg) within theinflatable cryogenic element 404. For example, the support structure 420may be configured such that the cross-sectional area of the infusionlumen 424 is less than that of the ventilation lumen 426.

The exemplary cryogenic surgical probe 400 illustrated in FIGS. 44-50also includes a plurality of temperature sensors, such as thermocouplesor thermistors. Referring more specifically to FIGS. 44 and 49, theexemplary implementation includes a first set of temperature sensors 446on the outer surface of one side of the inflatable cryogenic element 404and second set of temperature sensors 448 on the outer surface of theopposite side of the inflatable cryogenic element. Positioningtemperature sensors on the outer surface of the inflatable cryogenicelement 404 provides more accurate tissue temperature measurement thatinner surface positioning. In the exemplary implementation, thetemperature sensors in each set are arranged in a line, and the sets areabout 180 degrees apart.

The temperature sensors 446 and 448 are connected to signal wires 450which enter the signal wire lumen 428 by way of a series of signal wireapertures 452 on one side of the support structure 420. In the exemplaryimplementation, there are five (5) temperature sensors in each of thesets 446 and 448 and five (5) signal wire apertures 452 along one sideof the support structure 420. As all of the signal wires 450 enter thesignal wire lumen 428 on the same side of the support structure 420, thesignal wires 450 associated with the temperature sensors 448 wrap aroundthe support structure on their way to the associated signal wireapertures 452. Additionally, because some of the cryogenic fluid mayleak into the signal wire lumen 428 through the signal wire apertures452, the proximal end of the signal wire lumen is sealed with adhesive454 (FIG. 50). The adhesive fills in any gaps between the signal wires450 as well as any gaps between the signals wire and the inner surfaceof the signal wire lumen 428.

Proximal of the adhesive 454, the signal wire are twisted together andextend to a connector 456 in the handle 410. An electrical connectionbetween the handle connector 456 and the cryogenic fluid supply andcontrol apparatus 200 with the aforementioned cable 214.

The exemplary cryogenic surgical probe 400 may be reconfigured in avariety of ways. By way of example, but not limitation, in onealternative surgical probe, the ventilation lumen 426 and ventilationtube 434 are eliminated and the outlet aperture 442 is positioned nearthe center of the inflatable cryogenic element 404. An exteriorventilation lumen similar to the ventilation lumen 112 (FIG. 1) thatextends a short distance into the longitudinal end of the cryogenicelement 404 may be provided to ventilate the cryogenic fluid. Cryogenicsurgical probes in accordance with the present inventions may also beprovide with an insulative backing over a portion of the inflatablecryogenic element 404 in order to protect non-target tissue and increasethe efficiency of the probe. Such an insulative backing could, forexample, cover one-half of the surface area of the cryogenic element404. Here, one of the temperature sensor sets may be eliminated.Additionally, should applications so require, any of the features of theinflatable cryogenic elements discussed in Section II (e.g. the supportstructure 136 or the outer fluid transmission space 109) may beincorporated into the inflatable cryogenic elements 404.

Although the inventions disclosed herein have been described in terms ofthe preferred embodiments above, numerous modifications and/or additionsto the above-described preferred embodiments would be readily apparentto one skilled in the art. It is intended that the scope of the presentinventions extend to all such modifications and/or additions and thatthe scope of the present inventions is limited solely by the claims setforth below.

1-37. (canceled)
 38. An apparatus, comprising: an inflatable cryogenicelement; and a base member that carries the inflatable cryogenicelement, is pre-shaped into a loop configuration, and is bendable into anon-loop configuration.
 39. An apparatus as claimed in claim 38, whereinthe base member comprises an insulative base member.
 40. An apparatus asclaimed in claim 38, wherein the base member has a thermal conductivityof less than about 0.002 w/cm-K.
 41. An apparatus as claimed in claim38, wherein the base member comprises a foam member and a reinforcingmember that is pre-shaped into the loop configuration.
 42. An apparatusas claimed in claim 38, wherein the inflatable cryogenic element definesa longitudinal axis and a perimeter extending around the longitudinalaxis; the base member defines a surface; and the inflatable cryogenicelement is flattened against the base member surface such that asubstantial portion of the perimeter is adjacent the base membersurface.
 43. An apparatus as claimed in claim 38, wherein the inflatablecryogenic element includes an inlet and an outlet.
 44. An apparatus asclaimed in claim 43, wherein the inflatable cryogenic element defineslongitudinal ends and the inlet and outlet are each associated with arespective one of the longitudinal ends.
 45. An apparatus as claimed inclaim 43, further comprising: an infusion lumen associated with theinlet; and a ventilation lumen associated with the outlet.
 46. Anapparatus as claimed in claim 38, further comprising: a supportstructure located within the inflatable cryogenic element.
 47. Anapparatus as claimed in claim 46, wherein the support structure comprisea coil.
 48. An apparatus as claimed in claim 38, wherein the inflatablecryogenic element defines a length, a width, a height, and a width toheight ratio that is at least 2 to
 1. 49. An apparatus as claimed inclaim 38, wherein the base member defines longitudinal end portions, theapparatus further comprising: a connector associated with thelongitudinal end portions of the base member.
 50. An apparatus asclaimed in claim 49, wherein the connector comprises first and secondportions that respectively extend longitudinally beyond the first andsecond longitudinal ends of the base member.
 51. An apparatus as claimedin claim 38, further comprising: a longitudinally movable insulationsleeve.
 52. An apparatus as claimed in claim 38, wherein the base memberdefines a longitudinally extending lumen, the apparatus furthercomprising: a longitudinally movable stylet positionable within thelongitudinally extending lumen, the stylet being configured to maintainthe base member in the non-loop orientation when within thelongitudinally extending lumen.
 53. An apparatus as claimed in claim 38,wherein the base member and stylet define respective lengths and thestylet is at least as long as the base member.
 54. An apparatus asclaimed in claim 38, wherein the longitudinally movable stylet isconfigured to maintain the base member in a substantially straightorientation when within the longitudinally extending lumen.
 55. Anapparatus as claimed in claim 38, wherein the inflatable cryogenicelement comprises an outer tube and an inner tube located within theouter tube.
 56. An apparatus as claimed in claim 55, further comprising:a support structure located within the inner tube.
 57. An apparatus asclaimed in claim 55, wherein the outer tube includes an inlet and anoutlet and the inner tube includes an inlet and an outlet, the apparatusfurther comprising: first infusion and ventilation lumens respectivelyassociated with the outer tube inlet and outlet; and second infusion andventilation lumens respectively associated with the inner tube inlet andoutlet.
 58. A method of forming a lesion in tissue, comprising the stepsof: bending an apparatus including an inflatable cryogenic element intoa looped orientation around a tissue structure with a pre-shaped portionof the apparatus; maintaining the apparatus in the looped orientation;and directing cryogenic fluid through the inflatable cryogenic element.59. A method as claimed in claim 58, wherein the step of bending anapparatus comprises bending an apparatus, including an inflatablecryogenic element and an insulation element, into a looped orientationaround a tissue structure with a pre-shaped portion of the apparatussuch that the inflatable cryogenic element is in contact with targettissue and the insulation element is between the inflatable cryogenicelement and non-target tissue.
 60. A method as claimed in claim 58,wherein the step of bending an apparatus comprises the steps of:positioning an apparatus, including an inflatable cryogenic element, areinforcing member pre-shaped into a looped orientation, and a stylet,adjacent to a tissue structure; and advancing the apparatus distallywhile removing the stylet from the apparatus so the pre-shapedreinforcing member bends the apparatus into the looped orientation. 61.A method as claimed in claim 58, wherein the inflatable cryogenicelement includes first and second longitudinal end portions and the stepof directing cryogenic fluid comprises directing cryogenic fluid intothe first longitudinal end portion, through the inflatable cryogenicelement, and out of the second longitudinal end portion.
 62. A method asclaimed in claim 58, wherein the step of directing cryogenic fluidcomprises directing super-cooled liquid through the inflatable cryogenicelement.
 63. A method as claimed in claim 58, wherein the step ofbending an apparatus comprises bending an apparatus including aninflatable cryogenic element into a looped orientation around at leastone pulmonary vein.
 64. A system, comprising: a source of cryogenicfluid; and an apparatus including an inflatable cryogenic elementadapted to be operably connected to the source of cryogenic fluid, and abase member that carries the inflatable cryogenic element, is pre-shapedinto a loop configuration, and is bendable into a non-loopconfiguration.
 65. A system as claimed in claim 64, wherein the basemember comprises a foam member and a reinforcing member that ispre-shaped into the loop configuration.
 66. A system as claimed in claim64, wherein the base member comprises an insulative base member.
 67. Asystem as claimed in claim 64, wherein the inflatable cryogenic elementdefines a longitudinal axis and a perimeter extending around thelongitudinal axis; the base member defines a surface; and and theinflatable cryogenic element is flattened against the base membersurface such that a substantial portion of the perimeter is adjacent thebase member surface.
 68. A system as claimed in claim 64, wherein thesource of cryogenic fluid includes an inlet and an outlet; theinflatable cryogenic element includes an infusion lumen adapted to beconnected to the outlet and a ventilation lumen adapt to be connected tothe inlet.
 69. A system as claimed in claim 64, further comprising: asupport structure located within the inflatable cryogenic element.